Any update on when ULA will fly the first dual engine Centaur on Atlas V?

A potential TBD LEO flight next year is last I've heard. No word if its an NROL, NASA or Commercial payload and which range it fly from. If another Cygnus flight on Atlas occurs it would be a great test method as OA have said CRS-2 can fly in all 4-metre configs and a launch would be to ISS on same trajectory.

Right, I got the picture. However, according to ULA the first digit refers to the fairing diameter, not if the Centaur is encapsulated or not (which is a natural byproduct of the fairing variant used of course). So if they use no fairing at all it's kind of misleading to designate the variant 422 imho.

In the Starliner configurtion, the Centaur is not inside a failring, so 4XX.

Nope. There used to be an Atlas V 300 configuration as well (would've been used both for narrow payloads on Atlas V-Centaur, and all payloads for Atlas V Lite (Atlas V-Agena 2000). 400/500 just means the fairing diameter

In the Starliner configurtion, the Centaur is not inside a failring, so 4XX.

Nope. There used to be an Atlas V 300 configuration as well (would've been used both for narrow payloads on Atlas V-Centaur, and all payloads for Atlas V Lite (Atlas V-Agena 2000). 400/500 just means the fairing diameter

and there was also early option that would have been called AV-200 for DII class payloads, but was dropped in favor of would have been called AV-300 config that ended up being named AV-401 config.

The names during EELV development were:MLV-D: The Common Core Booster with SUS (Storable Upper Stage with Athena-based engine), 11 ft PLF. The "D" was for Delta-class payloads.MLV-A: The Common Core Booster with Centaur (Stretched Centaur II with RL10A-4), LPF, EPF, and maybe the 11 ft PLF if needed.

When SUS went away, MLV-G appeared. This was the additional of solids and the 5-meter PLF.

Then the Atlas V name was chosen.MLV-A became 401 with only LPF, EPF, and eventually an XPF. The 11 ft PLF was already off the table.Then 4xx came to be.MLV-G became the 5xx seriesHLV-G just became Atlas HLV or Atlas HVY

Edit: Thinking a little more about this, HLV-D might have actually been called HLV-L (L for LEO).

That's interesting, because when Lockheed ceded the small payload market to Delta II (mostly NASA missions segment) the plan was to just use the 401 for the GPS, DMSP, and DSCS, and other MLV-II class payloads. It was cheaper to just use the 401 than have another smaller/cheaper upper stage. At that same time, the decision was made to eliminate the 3-m PLF as well, because it's expensive to produce another diameter PLF, but not to add plugs or remove plugs form the 4-m PLF if need be.Now I'm wondering if Lockheed ever used the 300 naming convention, or just the government.

That's interesting, because when Lockheed ceded the small payload market to Delta II (mostly NASA missions segment) the plan was to just use the 401 for the GPS, DMSP, and DSCS, and other MLV-II class payloads.

That wasn't a Lockheed call. The USAF eliminated both EELV-S configurations from both contractors.

I asked this in the ULA thread, but perhaps it is more applicable here. Are there flight requirements for the DEC before they will put people on the rocket? And do we know when the DEC will first fly?

These requirements and difference across manufacturers are interesting. SpaceX is allowed their single 10x more powerful upper stage engine, but they seem to be required to do more testing of the final configuration than ULA despite ULA adding a whole engine to the design. Any input into the reasoning behind these requirements would be appreciated.

I asked this in the ULA thread, but perhaps it is more applicable here. Are there flight requirements for the DEC before they will put people on the rocket? And do we know when the DEC will first fly?

These requirements and difference across manufacturers are interesting. SpaceX is allowed their single 10x more powerful upper stage engine, but they seem to be required to do more testing of the final configuration than ULA despite ULA adding a whole engine to the design. Any input into the reasoning behind these requirements would be appreciated.

The DEC doesn't use two engines for safety - Two engines are needed for the required thrust. CST-100's will be heavy payloads for Atlas V, and they will also fly a different trajectory that requires more thrust.

I asked this in the ULA thread, but perhaps it is more applicable here. Are there flight requirements for the DEC before they will put people on the rocket? And do we know when the DEC will first fly?

These requirements and difference across manufacturers are interesting. SpaceX is allowed their single 10x more powerful upper stage engine, but they seem to be required to do more testing of the final configuration than ULA despite ULA adding a whole engine to the design. Any input into the reasoning behind these requirements would be appreciated.

The DEC doesn't use two engines for safety - Two engines are needed for the required thrust. CST-100's will be heavy payloads for Atlas V, and they will also fly a different trajectory that requires more thrust.

That makes a lot of sense. We saw how under powered the SEC is for LEO on OA-6. Still though, does Atlas V require testing with the DEC? Seems like a huge change.

DEC will first fly on the orbital flight test of the CST-100. Now it will be the first flight for this configuration on an Atlas V, but the DEC has flown on previous Atlas models, so they would argue that it has flight experience.

Still, Centaurs has gone through several upgrades and minor changes in the last 12(?) years since DEC last flew, so it won't be completely risk free. But they consider the OFT a sufficient demonstration, I guess.

The DEC is not the only change for human-rating. There is also the EDS system for detecting emergencies, and likely other smaller changes as well. Do we know if these have already been rolled into the standard Atlas production? Unlike a DEC, an EDS would be new, and I'd assume they (and NASA) would want more than one flight's worth of experience with it before launching a CST-100.